A "slotless" stator winding has bars which, instead of being wedged in the bottoms of slots formed in the magnetic circuit of the stator, are applied against the cylindrical inner surface thereof.
The system by which the bars are fixed requires some form of fixing means for fixing the bars to the stator magnetic circuit. Various fixing means e.g. screws or dovetail joints have been used. They engage the magnetic circuit and pull the bars radially outwards until they press against the inner surface of the magnetic circuit. Since the fixing means penetrate into the magnetic circuit to obtain a radial purchase thereon, the same fixing system can be used simultaneously to prevent the winding bars from moving tangentially, i.e. to prevent their angular positions from varying.
Known fixing systems for fixing bars to the magnetic circuit suffer from disadvantages such as:
They are not very compact because they use insulating screws whose poor mechanical characteristics require them to be of large dimensions.
Metal laminations are used in the rotor-stator air gap. These laminations constitute protruding bar-fixing teeth whose bases are dovetailed into the stator magnetic circuit. The metal laminations are not magnetic and provide good mechanical strength to the fixing teeth but they suffer losses by the Joule effect because of the high and variable magnetic inductions (see FIG. 8 of U.S. Pat. No. 3,405,297 in the name of Madsen).
The greater the number of wedges to be driven in radially, tangentially or longitudinally in known devices to make the bars both tangentially and radially motionless relative to the teeth, the longer and more expensive both assembly and disassembly.
The present invention aims to provide dovetailed teeth for use in a system for fixing stator winding bars of an electric rotating machine while avoiding the use of metal in the rotor-stator air gap.